Aside from the events that take place as part of the Olympics, it seems the competition is also on for each Games to become “greener” than those that have gone before. This year’s Olympic Winter Games in Vancouver boasted a variety of green initiatives, including Canada's biggest "living roof." London looks set to outdo Vancouver in 2012, but Rio is looking to up the ante again and be the first zero-carbon footprint games when it hosts the Summer Olympics in 2016. To help the city achieve this goal Swiss-based RAFAA Architecture and Design has proposed a Solar City Tower which features an eye-catching energy-generating waterfall.